JUnit test — analysing expected Exceptions [duplicate]

Answer 1

Look at fluent-exception-rule, it "combines Junit ExpectedException rule and AssertJ's assertions convenience. "

import pl.wkr.fluentrule.api.FluentExpectedException;
...
@Rule
public FluentExpectedException thrown = FluentExpectedException.none();

@Test
public void testDoSomethingCritical() {
    thrown.expect(CriticalServerException.class).hasMessage("Expected Message").hasNoCause();
    obj.doSomethingCritical();
}

Answer 2

I don't think there is a way of doing it using annotation. You may have to fall back to try-catch way where in the catch block you can verify the message

Answer 3

try
{
    // your code

    fail("Didn't throw expected exception");
}
catch(CriticalServerException e)
{
    assertEquals("Expected message", e.getMessage());
}

Answer 4

Java 8 solution

Here is a utility function that I wrote:

public final <T extends Throwable> T expectException( Class<T> exceptionClass, Runnable runnable )
{
    try
    {
        runnable.run();
    }
    catch( Throwable throwable )
    {
        if( throwable instanceof AssertionError && throwable.getCause() != null )
            throwable = throwable.getCause(); //allows "assert x != null : new IllegalArgumentException();"
        assert exceptionClass.isInstance( throwable ) : throwable; //exception of the wrong kind was thrown.
        assert throwable.getClass() == exceptionClass : throwable; //exception thrown was a subclass, but not the exact class, expected.
        @SuppressWarnings( "unchecked" )
        T result = (T)throwable;
        return result;
    }
    assert false; //expected exception was not thrown.
    return null; //to keep the compiler happy.
}

(taken from my blog)

Use it as follows:

@Test
public void testThrows()
{
    RuntimeException e = expectException( RuntimeException.class, () -> 
        {
            throw new RuntimeException( "fail!" );
        } );
    assert e.getMessage().equals( "fail!" );
}

Also, if you would like to read some reasons why you should not want to check the message of your exception, see this: https://softwareengineering.stackexchange.com/a/278958/41811

Answer 5

try {
    // test code invacation
    fail("Exception not throw!!!");
} catch(CriticalServerException ex) {
    assertTrue("Invalid exception data", ex.toString().contains("error text"));
}

Answer 6

If you have JUnit 4.7 or above try ExpectedException

There is an example in this question, which is copied below:

@Rule
public ExpectedException exception = ExpectedException.none();

@Test
public void testRodneCisloRok(){
    exception.expect(IllegalArgumentException.class);
    exception.expectMessage("error1");
    new RodneCislo("891415",dopocitej("891415"));
}